I. Field of the Invention
The present invention relates to techniques of analysis, particularly of hydrocarbons and substituted hydrocarbon mixtures generally classified in Class 250.
II. Description of the Prior Art
There are a number of ASTM (American Society for Testing Materials) and other standard methods for the analysis of physical properties of hydrocarbons such as ASTM D-86 distillation temperatures at various percentages distilled; ASTM D-1298 test for API gravity; Gas chromatography --Mass spectrometry (GC Mass Spec) for determination of weight percent aromatics; and ASTM D-2622 for sulfur.
Conventionally, these tests are conducted by enough different test apparatus to fill a small laboratory and are time-consuming and relatively expensive, particularly when applied to the hundreds of samples per day which may be required to be analyzed in a typical refinery. This situation will be made much more acute with the new reformulated fuel requirements for the prediction of total air pollutants (TAPs) exhaust benzene, volatile organic carbon (VOC), nitrogen oxides (NOx), Reid vapor pressure (RVP), and driveability index. Reformulated gasoline is defined in the Federal Register (59CFR32): ". . . any gasoline whose formulation has been certified under .sctn.80.40, which meets each of the standards and requirements prescribed under .sctn.80.41, and which contains less than the maximum concentration of the marker specified in .sctn.80.82 that is allowed for reformulation under .sctn.80.82." Effective Jan. 1, 1995, U.S. goverment regulations require these to be calculated by a "simple" model.
Simple Model PA1 Exhaust Benzene=1.884+0.949(Vol % Benzene)+0.113(Vol % Aromatics-Vol % Benzene) PA1 Total Toxics=Exhaust Benzene+Refueling Benzene+Evaporative Benzene+Running Loss Benzene+Butadiene+Formaldehyde+Acetaldehyde+POM PA1 Exhaust VOC=0.444[=0127/2.7)(sum of Wt % Oxygen from MTBE, ETBE, TAME, ETAE) PA1 Refueling VOC=0.04[0.1667(RVP)-0.45] PA1 Evaporative VOC=0.813-0.2393(RVP)+0.21239(RVP)(RVP) PA1 Running Loss VOC=0.2963-0.1306(RVP)+0.016255(RVP)(RVP)
______________________________________ Refueling Benzene = Vol % Benzene (Refueling VOC) (10) [1.3972 - 0.591 (MTBE Wt % Oxygen/2) - 0.081507 (RVP)] Evaporative Benzene = Vol % Benzene (10) (Evaporative VOC) {0.679 [1.4448 - 0.0684 (MTBE Wt % Oxygen/2 - 0.080274 (RVP)]} + 0.0321 [1.3758 - 0.579 (MTBE Wt % Oxygen(2) - 0.080274 (RVP)] Running Loss Benzene = Vol % Benzene (Running loss VOC) (10) [1.4448 - 0.684 (MTBE Wt % Oxygen/2) - 0.080274 (RVP) Butadiene = 0.00556 (Exhaust VOC) 1000 Formaldehyde = 0.01256 (Exhaust VOC) 1000 [1 + (0.421/2.7) (MTBE Wt % Oxygen + TAME Wt % Oxygen + (0.358/3.55 (EtOH Wt % Oxygen) + 0.137/2.7) (ETBE Wt % Oxygen + ETAE Wt % Oxygen)] Acetaldehyde = 0.00891 (Exhaust VOC) 1000 [1 + (0.078/2.7) (MTBE Wt % Oxygen + TAME Wt % Oxygen) + (0.865/3.55) (EtOH Wt % Oxygen) + 0.867/2.7) (ETBE Wt % Oxygen + ETAE Wt % Oxygen)] POM = 3.15 (Exhaust VOC) ______________________________________
At some time in the future, government regulators may require a more sophisticated "complex" model for prediction of these environmental parameters of fuels. The complex model contains more detailed calculations and two additional parameters: Total NOx (Nitrogen Oxides) and Total VOC (Volatile Organic Carbon). Since individual refineries will have to certify the VOC, NOx, TAP, benzene, and RVP of their fuels on a daily or more frequent basis, the number of tests and their complexity will pose a daunting problem to the refinery industry.
Chemometric models obtained may be used with a laboratory spectrophotometer to determine component concentrations or from physical properties of test samples. Alternatively, an on-line spectrometer installed on or "at" a gasoline stream may be used to predict real time concentrations and physical properties.
A significant amount of work has been done on use of spectroscopy to determine fuel properties.
U.S. Pat. No. 4,963,745 to Maggard teaches octane measured by NIR methyne band, etc.; U.S. Pat. No. 5,223,714 to Maggard teaches a prediction of octane, etc., using linear addition with or without NIR; U.S. Pat. No. 5,349,188 to Maggard teaches the determination of octane by secondary wavelengths in the NIR; U.S. Pat. No. 5,349,189 to Maggard teaches PIANO determination by NIR; U.S. Pat. No. 5,243,546 to Maggard teaches transfer of calibration equations in the NIR; U.S. Pat. No. 5,145,785 to Maggard et al. teaches aromatic content of diesel measured by NIR; U.S. Pat. No. 5,370,790 to Maggard et al. teaches aromatic content of diesel measured by NIR and relates to the apparatus; U.S. Pat. No. 5,348,645 to Maggard et al. teaches the measurement of sulfur content of diesel fuels by NIR; U.S. Pat. No. 5,362,965 to Maggard teaches the direct relationship between the second derivative of the NIR data and concentration of the component.
Experience Leads to Accurate Design of NIR Gasoline Analysis Systems, Welch, Bain, Maggard, and May, Oil & Gas Journal, Jun. 27, 1994, pp 48-56, determines research octane, motor octane, road octane, aromatics, olefins, RVP, benzene, oxygen content, and distillation points during gasoline blending.
U.S. Pat. No. 5,596,196, John B. Cooper et al., teaches Oxygenate Analysis and Control by Raman Spectroscopy.
Reformulated gasoline (RFG) testing thus involves measuring sulfur, olefin, aromatic contents, Reid Vapor Pressure (RVP), and benzene, distillation properties, plus total air pollutants (TAPs), exhaust benzene, volatile organic carbon (VOC), and nitrogen oxides (NOx). Measuring driveability, although not required, is desirable.
All of these tests can be conducted by using a spectrometer, preferably in the IR range, more preferably in the NIR range, and most preferably by a single instrument operating at high-correlation wavelengths. Measured Raman intensities may also be used. Importantly, VOC, TAP, exhaust benzene, NOx, and RVP may be correlated to IR absorbance at certain bands. Statistical methods including partial least squares analysis (PLS), multiple linear regression analysis (MLR), principal component regression analysis (PCR), and neural networks can be used and derivatives of first, particularly second, or other orders can be used. Level 3 or 4 SIMCA may be utilized. As used hereinafter, the term "SIMCA" is employed as commonly understood to refer to soft independent modeling of class analogy. Results can be displayed on a single screen. By predicting simple or complex EPA model values measured by the present invention (NIR, Mid-IR, or Raman embodiments) and comparing the results with results obtained by inserting laboratory values measured by conventional methods into the EPA model, the present invention remains accurate while providing the advantage of labor saving discussed above.